[Technical Field]
This invention relates to a method of manufacturing a puffed food, i.e. a food expanded by leavening, More particularly, the invention relates to a method of manufacturing a puffed food containing soybean protein to a high degree.
[Prior Art]
Hitherto, it has been widely known to manufacture puffed foods, such as breads, cookies, and cakes, by heating or baking a mixture including starch or cereal flour, such as wheat flour, as a main ingredient.
Recently, people are increasingly becoming interested in varieties of health food in the light of various troubles arising from habitual overeating of animal foods. In view of such trend and further of the recent aggravation of the world food situation, utilization of vegetable protein as a protein source has been seriously considered. Among various vegetable proteins, soybean protein is most useful for this purpose, because it is in far much larger production than others, and because it has an exceedingly better balance of essential amino acids and is of high nutritive value. Therefore, if soybean protein could be effectively utilized as a food ingredient, it would provide an excellent protein food which could substitute proteins obtainable from such domestic animal meats as beef and pork. From this point of view, attempts have been made to develop foods containing soybean protein to a high degree, and as a link of such efforts, possibilities of developing a puffed food have been studied. However, if a puffed food is produced from a mixture containing soybean portein as the only main ingredient, it lacks flavor or the ike and is thus far from meeting the requirement of tastefulness for a food. Therefore, the possibility of using as a principal ingredient a mixture of a cereal flour, such as wheat flour, and/or starch with soybean protein has been considered. However, in a conventional dough consisting of 100 parts by weight of hard flour, 2.5 parts by weight of yeast, 0.15 part by weight of yeast food, 5 parts by weight of refined white sugar, 2 parts by weight of common salt, 5 parts by weight of shortening, 2 parts by weight of dried skim milk, and 65 parts by weight of water, for example, a mere substitution of a soybean protein isolate for only a 10 wt.% portion of the 100 parts by weight of hard flour would result in too much stiffness of the dough and insufficient rollability thereof, the fermentation activity of the yeast being thus unfavorably affected. Further, when the dough is baked, the resulting bread would be an unsatisfactorily puffed one and would lack flavor and delicacy. Indeed, such bread could hardly meet the requirement of tastiness for a commercial food. As such, the prior-art attempts have not been successful in obtaining a puffed food containing a high proportion of a soybean protein isolate.